Treatment of gluten intolerance and related conditions

ABSTRACT

Provided herein are compositions, foods comprising nepenthesin or a derivative thereof and methods of using nepenthesin or a derivative thereof for modulating gluten intolerance and related conditions, such as celiac disease. Further provided herein are pharmaceutical compositions comprising nepenthesin or a derivative thereof and methods of using nepenthesin or a derivative thereof to treat bacterial infections of the gastrointestinal tract, such as  C. difficile  or  H. pylori . Further provided herein are compositions comprising recombinant nepenthesin I or nepenthesin II, or homologous proteins, and methods for making the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 13/843,369, filed on Mar. 15, 2013, now U.S. Pat. No. 9,005,610, which claims priority to the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application Ser. No. 61/729,210, filed Nov. 21, 2012, and U.S. Provisional Application Ser. No. 61/797,040, filed Nov. 27, 2012, each of which are hereby incorporated by reference in their entirety.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has been submitted in ASCII format via EFS-Web and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Jul. 3, 2013, is named 104069-0152 SL.txt and is 40,351 bytes in size.

FIELD OF THE INVENTION

Provided herein are compositions, foods and methods for the treatment of gluten intolerance and related conditions, such as celiac disease. Further provided herein are pharmaceutical compositions comprising nepenthesin or a derivative thereof and methods of using nepenthesin or a derivative thereof to treat bacterial infections of the gastrointestinal tract, such as C. difficile or H. pylori. Further provided herein are methods for using nepenthesin or a derivative thereof in hydrogen/deuterium exchange. Further provided herein are compositions comprising recombinant nepenthesin I or nepenthesin II, or homologous proteins, and methods for making the same.

BACKGROUND OF THE INVENTION

Ingestion of wheat, barley, rye and possibly oats, which contain gluten may cause abnormal autoimmune responses, such as celiac disease, wheat allergy and dermatitis herpetiformis, in gluten intolerant individuals. Gluten is a mixture of glutamine- and proline-rich glutenin and prolamin protein molecules. Most of the individuals having the abnormal autoimmune responses express the human leukocyte antigen (HLA) DQ2 or DQ8 molecules. The autoimmune reactions result in the development of small intestinal mucosal villous atrophy with crypt hyperplasia and mucosal inflammation. Symptoms of celiac disease can vary from individual to individual, and may include one or more of fatigue, chronic diarrhea, constipation, malabsorption of nutrients, weight loss, abdominal distension, anemia, as well as a substantially enhanced risk for the development of osteoporosis and intestinal malignancies (lymphoma and carcinoma).

Treatment for gluten intolerance commonly involves a lifelong strict gluten-free diet. However, gluten-free diet is inconvenient, restrictive, and gluten is difficult to avoid. Therefore, effective alternative treatments of gluten intolerance are needed.

A number of bacterial species are known to cause gastrointestinal tract infection. Although current treatment for such infections relies heavily on antibiotics, an increasing number of bacterial infections are found to be resistant to at least some antibiotics. In addition, some bacteria species form endospores that make them especially difficult to eradicate. Gastric proteases such as pepsin are generally unable to kill endospores, for example because of the inability to break down the proteinaceous coat that protects the endospore. Therefore, effective alternative treatments of bacterial infection are needed.

SUMMARY OF THE INVENTION

This invention relates to the discovery that the enzyme nepenthesin possesses a high proteolytic activity for cleaving proteins and oligopeptides (including gluten), especially at low pH (e.g., about 2 to 3). Nepenthesin (EC 3.4.23.12) is an aspartic protease of plant origin that can be isolated or concentrated from a variety of plant sources, such as the pitcher secretions of Nepenthes, a carnivorous pitcher plant, commonly known as monkey cups in tropical regions. Tökés et al., Digestive Enzymes Secreted by the Carnivorous Plant Nepenthes macferlanei L., Planta (Berl.) 119, 39-46 (1974). It has been found that the activity of nepenthesin is about 1000 fold higher than that of that of pepsin (EC 3.4.23.1), an enzyme present in the stomach of humans partly responsible for degrading food proteins into peptides. It has also been found that nepenthesin has a much more relaxed specificity than pepsin, efficiently cleaving after most amino acid residues with the exception of amino acid residues G, S, T, V, I and W. Notably, it cleaves after amino acid residues K, R and P. By comparison, pepsin presents high-efficiency cleavage for the hydrophobic amino acid residues F, L and M but cleavage after amino acid residues P, H, K and R is essentially forbidden.

Nepenthesin has two known isoforms: nepenthesin I (known to have two variants: nepenthesin Ia and nepenthesin Ib) and II. Both isoforms are found have a higher cleavage affinity for both amino acids P and Q than pepsin. Surprisingly, it has been discovered that the combination of nepenthesin I and nepenthesin II has a slightly different cleavage affinity than nepenthesin I alone. Specifically, extract comprising nepenthesin I and nepenthesin II cleaves more efficiently after the amino acid Q on the N-terminal side of gliadin and the amino acid P on the C-terminal side of gliadin than does nepenthesin I alone.

Gluten intolerance and associated conditions and symptoms, such as celiac disease and/or dermatitis herpetiformis, are caused by the patient's abnormal immune response to gluten in the small intestinal mucosa. Certain gluten components are resistant to cleavage by gastric and pancreatic peptidases such as pepsin, trypsin, chymotrypsin, and the like. While not wishing to be bound by any theories, it is contemplated that degradation of gluten to non-toxic peptides by nepenthesin prior to arriving at the intestinal tract of a patient decreases the levels of toxic gluten proteins or peptides going into the small intestine. As nepenthesin is acid stable, it is compatible with the stomach pH and digests gluten so as to modulate a patient's gluten intolerance or related conditions or symptoms.

Given its high activity at low pH and its broad spectrum of activity, nepenthesin is especially useful in digesting gluten proteins in the stomach. The degradation of gluten to non-toxic peptides is also referred to as detoxification of gluten. While not wishing to be bound by any theories, it is contemplated that degradation of gluten, which is comprised of proline- and glutamine-rich proteins, to non-toxic peptides can be more efficiently achieved by nepenthesin than by stomach enzymes such as pepsin.

This invention further relates to the use of nepenthesin, such as nepenthesin I and/or nepenthesin II and derivatives thereof in treating bacterial infections of the gastrointestinal tract. Given its high activity at low pH and its broad spectrum of activity, nepenthesin is useful in treating bacterial infections of the gastrointestinal tract. Without being bound by theory, it is believed that nepenthesin is more efficient than stomach enzymes at disrupting bacterial cell walls and endospore coats.

In one aspect, provided are methods for modulating gluten intolerance in a patient with gluten intolerance, which method comprises administering an effective amount of nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof to said patient. In one aspect, nepenthesin I or a derivative thereof is administered to said patient. In one aspect, nepenthesin II or a derivative thereof is administered to said patient. In one aspect, a mixture of nepenthesin I and nepenthesin II or derivatives thereof is administered to said patient.

In one embodiment, nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof is administered as a food additive such that nepenthesin or the derivative thereof is combined with gluten containing food to modulate or inhibit conditions associated with gluten intolerance. Nepenthesin or a derivative thereof can be used alone or in combination with such food. In one aspect, nepenthesin I or a derivative thereof is used. In one aspect, nepenthesin II or a derivative thereof is used. In one aspect, a mixture of nepenthesin I and nepenthesin II or derivatives thereof is used.

In another aspect, provided are methods for modulating a condition mediated by gluten intolerance in a patient which method comprises administering an effective amount of nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof to said patient. Such conditions include, by way of example only, celiac disease, wheat allergy, gluten sensitivity and/or dermatitis herpetiformis. In one aspect, nepenthesin I or a derivative thereof is administered to said patient. In one aspect, nepenthesin II or a derivative thereof is administered to said patient. In one aspect, a mixture of nepenthesin I and nepenthesin II or derivatives thereof is administered to said patient.

In any event, nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof can be administered to the patient prior to, concurrently with, or shortly after consumption of a food comprising gluten or suspected of comprising gluten. In one aspect, nepenthesin I or a derivative thereof is administered to said patient. In one aspect, nepenthesin II or a derivative thereof is administered to said patient. In one aspect, a mixture of nepenthesin I and nepenthesin II or derivatives thereof is administered to said patient.

In another aspect, provided are methods for modulating gluten intolerance or an associated condition, such as celiac disease, wheat allergy, gluten sensitivity or dermatitis herpetiformis, in a patient in need thereof, comprising treating a food comprising gluten or suspected of comprising gluten with an effective amount of nepenthesin prior to consumption by the patient. In one aspect, said food is treated with an effective amount of nepenthesin I or a derivative thereof. In one aspect, said food is treated with an effective amount of nepenthesin II or a derivative thereof. In one aspect, said food is treated with an effective amount of a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

In another aspect, provided are foods or compositions comprising nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof. In one aspect, said food or composition comprises nepenthesin I or a derivative thereof. In one aspect, said food or composition comprises nepenthesin II or a derivative thereof. In one aspect, said food or composition comprises a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

In another aspect, provided is a composition for optimizing cleavage of a gluten protein at a proline residue, comprising a mixture of recombinant nepenthesin I and recombinant nepenthesin II. In one aspect, provided is a composition for optimizing cleavage of a gluten protein at a glutamine residue, comprising a mixture of recombinant nepenthesin I and recombinant nepenthesin II.

In another aspect, provided is a composition comprising fragmented gluten, wherein the composition is enriched in gluten fragments produced by cleavage of the gluten at a proline residue of the gluten. In one aspect, provided is a composition comprising fragmented gluten, wherein the composition is enriched in gluten fragments produced by cleavage of the gluten at a glutamine residue.

In another aspect, provided is a method for digesting proteins comprising gluten which method comprises contacting said proteins with an effective amount of nepenthesin I and/or nepenthesin II.

In another aspect, provided is a method for producing recombinant nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof, the method comprising expressing in a chosen host organism a nucleic acid sequence which encodes said nepenthesin or homologue thereof and which nucleic acid sequence has been inserted into an appropriately designed vector; in order to obtain said nepenthesin or a homologue thereof. In one aspect, the recombinant nepenthesin is nepenthesin I or a derivative thereof. In one aspect, the recombinant nepenthesin is nepenthesin II or a derivative thereof. In one aspect, the recombinant nepenthesin is a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

In another aspect, provided is a composition comprising recombinant nepenthesin or a derivative thereof. In one aspect, the recombinant nepenthesin is recombinant nepenthesin I or a derivative thereof. In one aspect, the recombinant nepenthesin is recombinant nepenthesin II or a derivative thereof. In one aspect, the recombinant nepenthesin is a mixture of recombinant nepenthesin I and recombinant nepenthesin II or derivatives thereof.

In another aspect, provided are methods for preventing or treating bacterial or parasitic infections of the gastrointestinal tract in a patient, which method comprises administering a therapeutically effective amount of nepenthesin, such as nepenthesin I and/or nepenthesin II or a derivative thereof to said patient. In one aspect, nepenthesin I or a derivative thereof is administered to said patient. In one aspect, nepenthesin II or a derivative thereof is administered to said patient. In one aspect, a mixture of nepenthesin I and nepenthesin II or derivatives thereof is administered to said patient.

These and other aspects of the invention will be further described in the text that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows nepenthesin cleavage preferences at (A) the P1 or N-terminal side of the cleavage site and at (B) the P1′ or C-terminal side of the cleavage site. Data is grouped according to amino acid type and compared to a similar rendering of pepsin data from Hamuro et al. Specificity of immobilized porcine pepsin in H/D exchange compatible conditions. Rapid Communications in Mass Spectrometry 22(7):1041-1046 (2008). Hatched bars indicate nepenthesin digestion and the white bars pepsin digestion. The % cleavage represents the number of observed cleavages at the given residue, relative to the total number of the given residues in the set. Nepenthesin data were obtained from digests of six denatured proteins, as described in Example 2.

FIG. 2 shows an XRCC4 (SEQ ID NO:2) composite peptide sequence map, arranged according to domain type. The peptides were obtained using pepsin digestion at four different enzyme:substrate ratios (65:1 to 520:1, white/top set of bars), and using nepenthesin digestion at four different enzyme:substrate ratios (0.0075:1 to 0.38:1, spotted/bottom set of bars). FIGS. 2A and 2B represent the head region of XRCC4, and FIGS. 2C and 2D represent the tail and stalk regions of XRCC4.

FIG. 3 shows the average MASCOT score of peptides obtained after nepenthesin digestion, grouped by C-terminal amino acid. The number of peptides used for each calculation is associated with the terminal amino acid, above the bar. Peptides were obtained from the digests of six denatured proteins, as described in Example 2.

FIG. 4 shows peptide ion chromatograms (PICs) of XRCC4 digested with (A) nepenthesin and (B) pepsin over a range of enzyme:substrate ratios (shown in the legend). PICs for enzymatic digestion were generated from the same mass-load of substrate on column.

FIG. 5 shows the average length of all peptides identified from a nepenthesin digestion of gliadin from wheat, using LC-MS/MS, after 1, 5, 10, 15, 30, 60, 130, 360 or 810 minutes at 37° C. A 95% confidence cut-off (p<0.05) on the scores were used to remove false positive identification. Relative standard deviation of the peptide length is shown in the inset figure.

FIG. 6 displays the number of peptides identified by LC-MS/MS after 1, 5, 10, 15, 30, 60, 130, 360 or 810 minutes digestion at 37° C., grouped by length. Data as in FIG. 5.

FIG. 7 displays the same data as in FIG. 5, as a probability of obtaining a certain length after 10, 60, 120, 360 or 810 minutes digestion at 37° C.

FIG. 8 shows nepenthesin cleavage preferences at (A) the P1 or N-terminal side of the cleavage site and at (B) the P1′ or C-terminal side of the cleavage site. Left bars for each reside indicate digestion with nepenthesin extract, the middle bars indicate digestion with purified nepenthesin extract, and the right bars with recombinant nepenthesin I. The % cleavage represents the number of observed cleavages at the given residue, relative to the total number of peptides present. Nepenthesin data were obtained from digests of gliadin, as described in Example 9.

FIG. 9 shows an alignment of the protein sequences for nepenthesin I from Nepenthes mirabilis (SEQ ID NO: 3), Nepenthes gracilis (SEQ ID NO: 5), Nepenthes alata (SEQ ID NO: 4), Zea mays (SEQ ID NO: 8), and Oryza sativa (SEQ ID NO: 9), and nepenthesin II from Nepenthes mirabilis (SEQ ID NO: 6), Nepenthes gracilis (SEQ ID NO: 7), Zea mays (SEQ ID NO: 11), and Oryza sativa (SEQ ID NO: 10).

FIG. 10 shows a phylogenetic tree indicating the relatedness of nepenthesin proteins between different species.

DETAILED DESCRIPTION OF THE INVENTION I. Definitions

Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods, devices, and materials are now described. All technical and patent publications cited herein are incorporated herein by reference in their entirety. Nothing herein is to be construed as an admission that the invention is not entitled to antedate such disclosure by virtue of prior invention.

The practice of the present disclosure employs, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry and immunology, which are within the skill of the art. Such techniques are explained fully in the literature for example in the following publications. See, e.g., Sambrook and Russell eds. MOLECULAR CLONING: A LABORATORY MANUAL, 3^(rd) edition (2001); the series CURRENT PROTOCOLS IN MOLECULAR BIOLOGY (F. M. Ausubel et al. eds. (2007)); the series METHODS IN ENZYMOLOGY (Academic Press, Inc., N.Y.); PCR 1: A PRACTICAL APPROACH (M. MacPherson et al. IRL Press at Oxford University Press (1991)); PCR 2: A PRACTICAL APPROACH (M. J. MacPherson, B. D. Hames and G. R. Taylor eds. (1995)); ANTIBODIES, A LABORATORY MANUAL (Harlow and Lane eds. (1999)); CULTURE OF ANIMAL CELLS: A MANUAL OF BASIC TECHNIQUE (R. I. Freshney 5^(th) edition (2005)); OLIGONUCLEOTIDE SYNTHESIS (M. J. Gait ed. (1984)); Mullis et al. U.S. Pat. No. 4,683,195; NUCLEIC ACID HYBRIDIZATION (B. D. Hames & S. J. Higgins eds. (1984)); NUCLEIC ACID HYBRIDIZATION (M. L. M. Anderson (1999)); TRANSCRIPTION AND TRANSLATION (B. D. Hames & S. J. Higgins eds. (1984)); IMMOBILIZED CELLS AND ENZYMES (IRL Press (1986)); B. Perbal, A PRACTICAL GUIDE TO MOLECULAR CLONING (1984); GENE TRANSFER VECTORS FOR MAMMALIAN CELLS (J. H. Miller and M. P. Calos eds. (1987) Cold Spring Harbor Laboratory); GENE TRANSFER AND EXPRESSION IN MAMMALIAN CELLS (S. C. Makrides ed. (2003)) IMMUNOCHEMICAL METHODS IN CELL AND MOLECULAR BIOLOGY (Mayer and Walker, eds., Academic Press, London (1987)); WEIR'S HANDBOOK OF EXPERIMENTAL IMMUNOLOGY (L. A. Herzenberg et al. eds (1996)).

As used in the specification and claims, the singular form “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

As used herein, the term “comprising” is intended to mean that the compositions and methods include the recited elements, but not excluding others. “Consisting essentially of” when used to define compositions and methods, shall mean excluding other elements of any essential significance to the combination. For example, a composition consisting essentially of the elements as defined herein would not exclude other elements that do not materially affect the basic and novel characteristic(s) of the claimed invention. “Consisting of” shall mean excluding more than trace amount of other ingredients and substantial method steps recited. Embodiments defined by each of these transition terms are within the scope of this invention.

As used herein, the term “gluten” generally refers to the proteins present in wheat or related grain species, including barley and rye, which have potential harmful effect to certain individuals. Gluten proteins include gliadins such as α-gliadins, β-gliadins, γ-gliadins and ω-gliadins, which are monomeric proteins, and glutenins which are highly heterogeneous mixture of aggregates of high molecular weight and low-molecular-weight subunits held together by disulphide bonds. Many wheat gluten proteins have been characterized, see, for example, Woychik et al., Amino Acid Composition of Proteins in Wheat Gluten, J. Agric. Food Chem., 9(4), 307-310 (1961). The term gluten as used herein also includes oligopeptides that can be derived from normal human digestion of gluten proteins from gluten containing foods and cause the abnormal immune response. Some of these oligopeptides are resistant to normal digestive enzymes. Gluten, including the above-mentioned proteins and oligopeptides, is believed to act as antigens for T cells in celiac sprue in patients with gluten intolerance.

The term “nepenthesin” refers to the aspartic protease having the Enzyme Commission number EC 3.4.23.12, and includes all isoforms and variants of nepenthesin such as nepenthesin I and nepenthesin II, and recombinant nepenthesin, and salts thereof. Salts refer to those salts formed by nepenthesin with one or more base or one or more acid which retain the biological effectiveness and properties of the free nepenthesin, and which are not biologically or otherwise undesirable. Salts derived from inorganic bases include, but are not limited to, the sodium, potassium, lithium, ammonium, calcium, magnesium, iron, zinc, copper, manganese, aluminum salts and the like. Salts derived from organic bases include, but are not limited to, salts of primary, secondary, and tertiary amines, substituted amines including naturally occurring substituted amines, cyclic amines and basic ion exchange resins, such as isopropylamine, trimethylamine, diethylamine, triethylamine, tripropylamine, ethanolamine, 2-dimethylaminoethanol, 2-diethylaminoethanol, dicyclohexylamine, lysine, arginine, histidine, caffeine, procaine, hydrabamine, choline, betaine, ethylenediamine, glucosamine, methylglucamine, theobromine, purines, piperazine, piperidine, N-ethylpiperidine, polyamine resins and the like. Acids that can form salts include, but are not limited to, inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and the like, and organic acids such as acetic acid, propionic acid, glycolic acid, pyruvic acid, oxalic acid, maleic acid, malonic acid, succinic acid, fumaric acid, tartaric acid, citric acid, benzoic acid, cinnamic acid, mandelic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, salicyclic acid and the like.

Nepenthesin derivatives include biological equivalents, fragments and extended nepenthesin, and salts thereof, that retain proteolytic activity. In some embodiments, nepenthesin derivatives include biological equivalents of nepenthesin. “Biological equivalents” include those having at least about 80% homology or identity or alternatively, at least about 85% , or alternatively at least about 90%, or alternatively at least about 95%, or alternatively 98% homology with nepenthesin, or alternatively a polypeptide or protein encoded by a polynucleotide that hybridizes under stringent conditions to the nucleotide sequence encoding nepenthesin or its complement, while maintaining the desired structure and exhibiting at least part of the proteolytic activity of nepenthesin.

In some embodiments, the nepenthesin derivative is a fragment of nepenthesin having at least about 20 contiguous amino acids of the full nepenthesin protein, or at least about 50 contiguous amino acids, or comprising 100 or more contiguous amino acids, up to the complete protein of nepenthesin. Nepenthesin derivatives also include nepenthesin having additional sequences.

In some embodiments, a nepenthesin derivative has at least about 10% of the proteolytic activity of nepenthesin, or at least about 50%, or at least about 70%, or at least about 90% of the proteolytic activity of nepenthesin or 100% or more of the proteolytic activity of nepenthesin.

As used herein, the term “biological equivalent thereof” is intended to be synonymous with “equivalent thereof” which when referring to a reference protein, antibody, polypeptide or nucleic acid, intends those having minimal homology while still maintaining desired structure or functionality. In an alternative embodiment, the term “biological equivalent of” a polynucleotide refers to one that hybridizes under stringent conditions to the reference polynucleotide or its complement. Unless specifically recited herein, it is contemplated that any polynucleotide, polypeptide or protein mentioned herein also includes equivalents thereof. For example, an equivalent intends at least about 80% homology or identity and alternatively, at least about 85%, or alternatively at least about 90%, or alternatively at least about 95%, or alternatively 98% percent, or alternatively 99% percent homology or sequence identity and exhibits substantially equivalent biological activity to the reference protein, polypeptide or nucleic acid.

A polynucleotide or polynucleotide region (or a polypeptide or polypeptide region) having a certain percentage (for example, 80%, 85%, 90%, or 95%) of “sequence identity” to another sequence means that, when aligned, that percentage of bases (or amino acids) are the same in comparing the two sequences. The alignment and the percent homology or sequence identity can be determined using software programs known in the art, for example those described in Current Protocols in Molecular Biology (Ausubel et al., eds. 1987) Supplement 30, section 7.7.18, Table 7.7.1. Preferably, default parameters are used for alignment. One alignment program is BLAST, using default parameters. Examples of the programs include BLASTN and BLASTP, using the following default parameters: Genetic code=standard; filter=none; strand=both; cutoff=60; expect=10; Matrix=BLOSUM62; Descriptions=50 sequences; sort by=HIGH SCORE; Databases=non-redundant, GenBank+EMBL+DDBJ+PDB+GenBank CDS translations+SwissProtein+SPupdate+PIR. Details of these programs can be found at the following Internet address: ncbi.nlm.nih.gov/cgi-bin/BLAST.

Suitable expression vectors include vectors capable of expressing a polynucleotide operatively linked to a regulatory element, such as a promoter region and/or an enhancer that is capable of regulating expression of such DNA. Thus, an expression vector refers to a recombinant DNA or RNA construct, such as a plasmid, a phage, recombinant virus or other vector that, upon introduction into an appropriate host cell, results in expression of the inserted DNA. Appropriate expression vectors include those that are replicable in eukaryotic cells and/or prokaryotic cells and those that remain episomal or those which integrate into the host cell genome.

As used herein, the term “vector” refers to a non-chromosomal nucleic acid comprising an intact replicon such that the vector may be replicated when placed within a cell, for example by a process of transformation. Vectors may be viral or non-viral. Viral vectors include retroviruses, adenoviruses, herpesvirus, papovirus, or otherwise modified naturally occurring viruses. Exemplary non-viral vectors for delivering nucleic acid include naked DNA; DNA complexed with cationic lipids, alone or in combination with cationic polymers; anionic and cationic liposomes; DNA-protein complexes and particles comprising DNA condensed with cationic polymers such as heterogeneous polylysine, defined-length oligopeptides, and polyethylene imine, in some cases contained in liposomes; and the use of ternary complexes comprising a virus and polylysine-DNA.

Non-viral vector may include plasmid that comprises a heterologous polynucleotide capable of being delivered to a target cell, either in vitro, in vivo or ex-vivo. The heterologous polynucleotide can comprise a sequence of interest and can be operably linked to one or more regulatory elements and may control the transcription of the nucleic acid sequence of interest. As used herein, a vector need not be capable of replication in the ultimate target cell or subject. The term vector may include expression vector and cloning vector.

“Homology” or “identity” or “similarity” refers to sequence similarity between two peptides or between two nucleic acid molecules. Homology can be determined by comparing a position in each sequence which may be aligned for purposes of comparison. When a position in the compared sequence is occupied by the same base or amino acid, then the molecules are homologous at that position. A degree of homology between sequences is a function of the number of matching or homologous positions shared by the sequences. An “unrelated” or “non-homologous” sequence shares less than 40% identity, or alternatively less than 25% identity, with one of the sequences of the present disclosure.

“Hybridization” refers to hybridization reactions that can be performed under conditions of different “stringency”. Conditions that increase the stringency of a hybridization reaction are widely known and published in the art: see, for example, Sambrook and Russell eds. (2001) Molecular Cloning: A Laboratory Manual, 3rd edition. Examples of relevant conditions include (in order of increasing stringency): incubation temperatures of 25° C., 37° C., 50° C., and 68° C.; buffer concentrations of 10×SSC, 6×SSC, 1×SSC, 0.1×SSC (where SSC is 0.15 M NaCl and 15 mM citrate buffer) and their equivalent using other buffer systems; formamide concentrations of 0%, 25%, 50%, and 75%; incubation times from 5 minutes to 24 hours and washes of increasing duration, increasing frequency, or decreasing buffer concentrations.

In one embodiment, “therapeutically effective amount” refers to that amount of a compound that results in prevention or amelioration of symptoms in a patient or a desired biological outcome, e.g., improved clinical signs, delayed onset of disease, etc. The effective amount can be determined by one of ordinary skill in the art. The selected dosage level can depend upon the severity of the condition being treated, and the condition and prior medical history of the patient being treated. However, it is within the skill of the art to start doses of the compound at levels lower than required to achieve the desired therapeutic effect and to gradually increase the dosage until the desired effect is achieved.

“Concurrent administration,” or co-treatment, as used herein includes administration of the agents together, or before or after each other.

The term “modulate” or “modulating” means any treatment of a disease or disorder in a subject, such as a mammal, including:

-   -   preventing or protecting against the disease or disorder, that         is, causing the abnormal biological reaction or symptoms not to         develop;     -   inhibiting the disease or disorder, that is, arresting or         suppressing the development of abnormal biological reactions         and/or clinical symptoms; and/or     -   relieving the disease or disorder that is, causing the         regression of abnormal biological reactions and/or clinical         symptoms.

As used herein, the term “preventing” refers to the prophylactic treatment of a patient in need thereof. The prophylactic treatment can be accomplished by providing an appropriate dose of a therapeutic agent to a subject at risk of suffering from an ailment, thereby substantially averting onset of the ailment.

As used herein, the term “condition” refers to a disease state for which the compounds, compositions and methods provided herein are being used.

As used herein, the term “patient” or “subject” refers to mammals and includes humans and non-human mammals. In particular embodiments herein, the patient or subject is a human.

The term “about” when used before a numerical value indicates that the value may vary within a reasonable range, such as ±5%, ±1%, and ±0.2%.

II. Methods

In one aspect, provided are methods for modulating gluten intolerance in a patient with gluten intolerance which method comprises administering an effective amount of nepenthesin, such as nepenthesin I and/or nepenthesin II, or a derivative thereof to said patient.

In one embodiment, nepenthesin or a derivative thereof is administered as a food additive such that nepenthesin or a derivative thereof is combined with gluten containing food to modulate or inhibit conditions associated with gluten intolerance. Nepenthesin or a derivative thereof can be used alone or in combination with such food.

In another aspect, provided are methods for modulating a condition mediated by gluten intolerance in a patient which method comprises administering an effective amount of nepenthesin or a derivative thereof to said patient. Such conditions include by way of example only celiac disease, wheat allergy, gluten sensitivity and dermatitis herpetiformis. Nepenthesin or a derivative thereof can be administered to the patient prior to, concurrently with, or shortly after ingestion of a food comprising gluten or suspected of comprising gluten.

In some embodiments, nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof is administered to the patient prior to ingestion by the patient of the food comprising gluten or suspect of comprising gluten. In some embodiments, nepenthesin or a derivative thereof is administered within a period that nepenthesin or the derivative thereof is at least partially effective (for example, at least about 10%, 20%, 50%, 70%, 90% of original activity) in degrading gluten in the food that the patient will ingest. In some embodiments, nepenthesin or a derivative thereof is administered not more than about 4 hours, 3 hours, 2 hours, 1 hour, or 30 minutes prior to ingestion of the food by the patient.

In some embodiments, nepenthesin or a derivative thereof is administered to the patient concurrently with ingestion by the patient of the food comprising gluten or suspect of comprising gluten. In some embodiments, nepenthesin or a derivative thereof is administered with the food, such as an ingredient or additive to the food. In some embodiments, nepenthesin or a derivative thereof is administered separately from the food.

In some embodiments, nepenthesin or a derivative thereof is administered to the patient shortly after ingestion by the patient of the food comprising gluten or suspect of comprising gluten. In some embodiments, nepenthesin or a derivative thereof is administered within a period that at least part (for example, at least about 10%, 20%, 50%, 70%, 90%) of the gluten in the food is still in the stomach of the patient. In some embodiments, nepenthesin or a derivative thereof is administered not more than 4 hours, 3 hours, 2 hours, 1 hour, or 30 minutes after ingestion of the food by the patient.

In another aspect, provided are methods for preventing or treating bacterial or parasitic infections of the gastrointestinal tract in a patient, which method comprises administering a composition comprising an effective amount of nepenthesin or a derivative thereof to said patient. By way of example only, such bacterial infections may be caused by bacteria such as Bacillus cereus, Bacillus anthracis, Helicobacter pylori, Salmonella, Campylobacter, E. coli, Shigella, Clostridium difficile, Vibrio cholerae, Staphylococcus aureus, Clostridium perfringens, Clostridium botulinum, Campylobacter jejuni, and Listeria monocytogenes. In one aspect, said composition comprises nepenthesin I or a derivative thereof. In one aspect, said composition comprises nepenthesin II or a derivative thereof. In one aspect, said composition comprises a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

C. difficile are naturally-occurring intestinal flora in a small subset of the population. However, most people are exposed to C. difficile as patients in a hospital, nursing home, or similar facility by ingesting spores of the bacteria. C. difficile can overrun the gastrointestinal tract under opportunistic conditions, usually due to treatment with a broad-spectrum antibiotic which destroys the normal gut flora. The bacteria release toxins that can cause bloating, diarrhea, and severe abdominal pain. C. difficile infections are the most common cause of pseudomembranous colitis, which in rare cases progress to life-threatening toxic megacolon. The rate of C. difficile is acquired by a significant number of patients with long hospital stays: acquisition is estimated to be 13% in patients with hospital stays of up to two weeks, and 50% in those with hospital stays longer than four weeks. Clabots, C R; Johnson, S; Olson, M M; Peterson, L R; Gerding, D N (September 1992). “Acquisition of Clostridium difficile by hospitalized patients: evidence for colonized new admissions as a source of infection”. Journal of Infectious Diseases 166 (3): 561-7.

Helicobacter have been found living in the lining of the upper gastrointestinal tract, as well as the liver of mammals and some birds. H. pylori infects up to 50% of the human population and may be pathogenic to humans. H. pylori is strongly associated with peptic ulcers, chronic gastritis, duodenitis, and stomach cancer. Other Helicobacter species have also been associated with these conditions, including H. suis, H. felis, H. bizzozeronii and H. salomonis.

In one aspect, a therapeutically effective amount of the pharmaceutical composition of the invention is administered to a patient known to have or suspected of having an infection of the gastrointestinal tract. In another aspect, the composition is administered to a patient at risk of being infected, for example a patient with a long hospital stay and/or a patient who is prescribed a broad spectrum antibiotic.

Typically, nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof is administered in an amount that is safe and sufficient to produce the desired effect of gluten detoxification or treating bacterial infection. The dosage of the compounds of nepenthesin or derivatives thereof can vary depending on many factors such as the particular nepenthesin or derivative thereof administered, the patient's sensitivity to gluten, the amount and types of gluten containing food ingested, the pharmacodynamic properties, the mode of administration, the age, health and weight of the recipient, the nature and extent of the symptoms, the frequency of the treatment and the type of concurrent treatment, if any, and the clearance rate of the compound. One of skill in the art can determine the appropriate dosage based on the above factors. The compounds may be administered initially in a suitable dosage that may be adjusted as required, depending on the clinical response. The amount of nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof which will be effective in the treatment of a disease correlated with or caused by infection with pathogenic bacteria, for example, can be determined by standard clinical techniques based on the present description. In addition, in vitro assays may optionally be employed to help identify optimal dosage ranges. The precise dose to be employed in the formulation will also depend on the route of administration, and the seriousness of the disease or disorder, and should be decided according to the judgment of the practitioner and each subject's circumstances.

The dosage or dosing regime of an adult patient may be proportionally adjusted for children and infants, and also adjusted for other administration or other formats, in proportion for example to molecular weight or immune response. Administration or treatments may be repeated at appropriate intervals, at the discretion of the physician.

Generally, nepenthesin or a derivative thereof is administered when needed, such as when the patient will be or is consuming or has consumed a food comprising gluten or suspected of comprising gluten, or having or suspected of having a bacterial infection. Alternatively, a pharmaceutical composition comprising nepenthesin or a derivative thereof may be administered to a patient in need thereof. In any case, it can be administered in dosages of about 0.001 mg to about 1000 mg/kg body weight per day, or about 1 mg to about 100 g per dose for an average person. In some embodiments, nepenthesin or a derivative thereof can be administered at 0.001, 0.01, 0.1, 1, 5, 10, 50, 100, 500, or 1000 mg/kg body weight per day, and ranges between any two of these values (including endpoints). In some embodiments, nepenthesin or a derivative thereof can be administered at 1 mg, 10 mg, 100 mg, 200 mg, 500 mg, 700 mg, 1 g, 10 g, 20 g, 50 g, 70 g, 100 g per dose, and ranges between any two of these values (including endpoints). In some embodiments, it may be administered once, twice, three times, etc. a day, depending on the number of times the patient ingests a gluten containing food, or depending on the type, severity, or risk of bacterial or parasitic infection.

The compounds of this invention can be administered as the sole active agent or they can be administered in combination with other agents (simultaneously, sequentially or separately, or through co-formulation), including other compounds that demonstrate the same or a similar therapeutic activity and that are determined to safe and efficacious for such combined administration.

In some embodiments, nepenthesin or a derivative thereof is administered with another enzyme, such as a gastric protease (e.g., pepsin and pepsinogen), another aspartic protease, such as those described by Chen et al., Aspartic proteases gene family in rice: Gene structure and expression, predicted protein features and phylogenetic relation, Gene 442:108-118 (2009), and enzymes such as prolyl endopeptidase (PEP), dipeptidyl peptidase IV (DPP IV), and dipeptidyl carboxypeptidase (DCP) or cysteine proteinase B described in U.S. Pat. No. 7,910,541.

In some embodiments, nepenthesin is administered to the patient with another agent. Non-limiting examples of agents that can be administered with nepenthesin include inhibitors of tissue transglutaminase, anti-inflammatory agents such as HMG-CoA reductase inhibitors (e.g., compactin, lovastatin, simvastatin, pravastatin and atorvastatin), leukotriene receptor antagonists (e.g., montelukast and zafirlukast), COX-2 inhibitors (e.g., celecoxib and rofecoxib), p38 MAP kinase inhibitors (e.g., BIRB-796); mast cell-stabilizing agents such as sodium chromoglycate (chromolyn), pemirolast, proxicromil, repirinast, doxantrazole, amlexanox nedocromil and probicromil, anti-ulcer agents, anti-allergy agents such as anti-histamine agents (e.g., acrivastine, cetirizine, desloratadine, ebastine, fexofenadine, levocetirizine, loratadine and mizolastine), inhibitors of transglutaminase 2 (TG2), anti-TNFα agents, and antibiotics.

In some embodiments, nepenthesin is co-administered with an antibiotic, such as a penicillin, a cephalosporin, a carbapenem, a polymixin, a rifamycin, a lipiarmycin, a quinolone, a sulfonamide, a β-lactam, a fluoroquinolone, a glycopeptide, a ketolide, a lincosamide, a streptogramin, an aminoglycoside, a macrolide, a tetracycline, a cyclic lipopeptide, a glycylcycline, or an oxazolidinone. Antibiotics in these classes are known in the art.

In some embodiments, nepenthesin is co-administered with an anti-infective agent (for example, an antifungal triazole or amphotericin). These may include carbapenems, for example meropenem or imipenem, to broaden the therapeutic effectiveness.

Also provided herein is the use of nepenthesin or a derivative thereof in the manufacture of a medicament for the treatment or prevention of one of the afbrementioned conditions and diseases.

Compositions

Nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof can be administered in a variety of compositions alone or with appropriate, pharmaceutically acceptable carriers or diluents or dietary ingredients.

Accordingly, in another aspect, provided herein is a composition comprising nepenthesin or a derivative thereof. In some embodiments, the composition is an edible composition. In some embodiments, the composition is a dietary supplement. In some embodiments, the composition is a pharmaceutical composition. In some embodiments, the composition is a food or food additive. The compositions may be formulated into solid, semi-solid, or liquid forms, such as tablets, capsules, powders, granules, ointments, solutions, injections, gels, and microspheres. Administration of nepenthesin or a derivative thereof can be achieved in various ways, for example, by oral administration.

In some embodiments, the pharmaceutical compositions comprise a therapeutically effective amount of an agent and a pharmaceutically acceptable carrier. In a particular embodiment, the term “pharmaceutically acceptable” means approved by a regulatory agency of the federal or a state government or listed in the U.S. Pharmacopeia or other generally recognized pharmacopeia for use in animals, and more particularly in humans. The term “carrier” refers to a diluent, adjuvant, excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil and the like. Saline solutions and aqueous dextrose and glycerol solutions can also be employed as liquid carriers.

Suitable pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, ethanol and the like. The composition, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. These compositions can take the form of solutions, suspensions, emulsion, tablets, pills, capsules, powders, sustained-release formulations and the like. Examples of suitable pharmaceutical carriers are described in “Remington's Pharmaceutical Sciences” by E. W. Martin, incorporated in its entirety by reference herein. Such compositions will contain a therapeutically effective amount of nepenthesin or derivative thereof, preferably in purified form, together with a suitable amount of carrier so as to provide the form for proper administration to the subject. The formulation should suit the mode of administration.

For oral administration, nepenthesin or a derivative thereof can be used alone or in combination with appropriate additives to make tablets, powders, granules, capsules, syrups, liquids, suspensions, etc. For example, solid oral forms of nepenthesin or a derivative thereof can be prepared with conventional additives, disintegrators, lubricants, diluents, buffering agents, moistening agents, preservatives and flavoring agents. Non-limiting examples of excipients include lactose, mannitol, corn starch, potato starch, crystalline cellulose, cellulose derivatives, acacia, corn starch, sodium carboxymethylcellulose, talc, magnesium stearate, flavors and colors. In some embodiments, the formulation releases nepenthesin or a derivative thereof in the stomach of the patient so that gluten can be degraded by the nepenthesin or derivative thereof.

Nepenthesin or a derivative thereof can be lyophilized from an aqueous solution optionally in the presence of appropriate buffers (e.g. phosphate, citrate, histidine, imidazole buffers) and excipients (e.g. cryoprotectants such as sucrose, lactose, trehalose). Lyophilized cakes can optionally be blended with excipients and made into different forms.

In another aspect, provided are methods for treating gluten intolerance or an associated condition, such as celiac disease, wheat allergy, gluten sensitivity and dermatitis herpetiformis, in a patient in need thereof, comprising treating a food comprising gluten or suspected of comprising gluten with an effective amount of nepenthesin or a derivative thereof prior to consumption by the patient. In some embodiments, the food is combined with an effective amount of nepenthesin or a derivative thereof during its preparation, preferably after any heating steps.

In some embodiments, nepenthesin or a derivative thereof is administered as a food additive together with a food comprising gluten or suspected of comprising gluten, such as bread, pasta, cereal, and the like, made from wheat, rye and barley, etc. In some embodiments, nepenthesin or a derivative thereof is added as an ingredient in such food. In some embodiments, nepenthesin or a derivative thereof is dispersed into a food prior to consumption, optionally at a pH where it is inactive, such as a pH of about or above 5. In some embodiments, nepenthesin or a derivative thereof can be made or incorporated into a powder, a spread, a spray, a sauce, a dip, a whipped cream, etc., that can be applied to the gluten comprising food when the food is being consumed by a patient. In some embodiments, nepenthesin or a derivative thereof can be made into forms that appeal to one's appetite, such as candies, chewing gums, dietary supplement chews, syrup, etc. for easy administration. In some embodiments, nepenthesin or a derivative thereof can be mixed with common food items, such as sugar, salt, salad dressing, spices, cheese, butter, margarines, spreads, butter, frying shortenings, mayonnaises, dairy products, nut butters, seed butters, kernel butters, peanut butter, etc. Preferably, the food items or additives comprising nepenthesin do not require heating before being ingested by a patient so that possible loss of activity of nepenthesin or a derivative thereof due to elevated temperature can be minimized.

In another aspect, provided is a food product comprising nepenthesin or a derivative thereof. In some embodiments, the food product comprises gluten or is suspected of comprising gluten, such as bakery products (e.g., cakes, muffins, donuts, pastries, rolls, and bread), pasta, crackers, tortilla chips, cereal etc. made from wheat, rye and barley. In some embodiments, the food product can be consumed with another food product comprising gluten or suspected of comprising gluten. Non-limiting examples of such food include a powder, a spread, a spray, a sauce, a dip, a whipped cream, candies, chewing gums, syrup, sugar, salt, salad dressing, spices, cheese, butter, margarines, spreads, butter, frying shortenings, mayonnaises, dairy products, nut butters, seed butters, kernel butters, peanut butter, etc.

In some embodiments, the nepenthesin or derivative thereof is admixed with food, or used to pre-treat foodstuffs containing glutens. Nepenthesin present in foods can be enzymatically active to reduce the level of gluten in the food prior to or during ingestion.

In some embodiments, the composition (such as pharmaceutical composition or edible composition) or food product comprises from about 0.1% to about 99%, from about 0.5% to about 95%, from about 1% to about 95%, from about 5% to about 95%, from about 10% to about 90%, from about 20% to about 80%, from about 25% to about 75% of nepenthesin. In some embodiments, the nepenthesin in the composition (such as pharmaceutical composition or edible composition) or food product is about 0.01%, about 0.1%, about 0.5%, about 1%, about 5%, about 10%, about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, or about 95% of the total composition or food product, or a range between any two of the values (including end points).

In another aspect, provided is a composition for optimizing cleavage of a gluten protein at a proline residue, comprising a mixture of recombinant nepenthesin I and recombinant nepenthesin II. In one aspect, provided is a composition for optimizing cleavage of a gluten protein at a glutamine residue, comprising a mixture of recombinant nepenthesin I and recombinant nepenthesin II. In some embodiments, the composition is least about 20%, 50%, 2 times, 5, times or 10 times more effective in cleaving a gluten protein at a proline residue as compared to a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone. In some embodiments, the composition is least about 20%, 50%, 2 times, 5, times or 10 times more effective in cleaving a gluten protein at a glutamine residue as compared to a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone.

In another aspect, provided is a composition for optimizing cleavage of a protein at an amino acid residue(s), such as H, K, R, D, E, S, T, and/or N. In some embodiments, the composition is least about 20%, 50%, 2 times, 5, times or 10 times more effective in cleaving a protein at a given amino acid residue(s) as compared to a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone. In some embodiments, the composition is least about 10 times, 100 times, 500 times, 1000 times, 1400 times, or 2000 times or greater more effective in cleaving a protein at a given amino acid residue(s) as compared to a composition comprising a same amount or concentration of pepsin. In some embodiments, the residue is a residue that can be cleaved by pepsin. In some embodiments, the residue is a residue that is not efficiently cleaved by pepsin.

In another aspect, provided is a composition comprising fragmented gluten, wherein the composition is enriched in gluten fragments produced by cleavage of the gluten at a proline residue of the gluten. In one aspect, provided is a composition comprising fragmented gluten, wherein composition is enriched in gluten fragments produced by cleavage of the gluten at a glutamine residue. In some embodiments, the gluten fragments produced by cleavage of the gluten at a proline residue of the gluten is least 2 times, 5 times, or 10 times of the gluten fragments produced by cleavage of the gluten at a proline residue of the gluten by a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone. In some embodiments, the gluten fragments produced by cleavage of the gluten at a glutamine residue of the gluten is least 2 times, 5 times, 10 times of the gluten fragments produced by cleavage of the gluten at a glutamine residue of the gluten by a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone.

In another aspect, provided is a composition for optimizing cleavage of a protein at other amino acid residue(s), such as H, K, R, D, E, S, T, and/or N. In some embodiments, the protein fragments produced by cleavage of the protein at a given amino acid residue(s) of the protein is least 2 times, 5 times, or 10 times of the protein fragments produced by cleavage of the protein at the given amino acid residue(s) of the protein by a composition comprising a same amount or concentration of either nepenthesin I or nepenthesin II alone. In some embodiments, the protein fragments produced by cleavage of the protein at a given amino acid residue(s) of the protein is least about 10 times, 50 times, 500 times, 1000 times, 1400 times, or 2000 times or greater of the protein fragments produced by cleavage of the protein at the given amino acid residue(s) of the protein by a composition comprising a same amount or concentration of pepsin. In some embodiments, the residue is a residue that can be cleaved by pepsin. In some embodiments, the residue is a residue that is not efficiently cleaved by pepsin.

Methods of Preparation

Nepenthesin can be concentrated (or extracted) or purified by known methods, such as filtration or affinity purification based on immobilized pepstatin, from a natural source, such as pitcher secretions of plants such as Nepenthes. Nepenthesin I and II are found in relatively small quantity in natural plant secretions. Production of nepenthesin I and/or nepenthesin II can be increased, for example, using bioengineering technologies to create transgenic plants that express and/or secrete increased amounts of nepenthesin I or nepenthesin II, or a derivative thereof.

Besides being isolated from a plant source, nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof may be prepared by chemical synthesis. Chemical synthesis can be achieved by coupling of the amino acids according to the sequence of nepenthesin. Various peptide coupling methods and commercial peptide synthetic apparatuses are available to synthesis peptide or proteins, for example, automated synthesizers by Applied Biosystems, Inc., Foster City, Calif., Beckman, and other manufacturers.

In another aspect, provided is a method of preparing nepenthesin using recombinant production systems by transforming or transfecting a cell with the DNA and/or messenger RNA of nepenthesin so that the cell is capable of producing nepenthesin. For example, nepenthesin can be produced by establishing host-vector systems in organisms such as Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, Lactobacillus, Bacilli, Aspergilli, and plant cell cultures, such as tobacco cells, etc.

Vectors and host cells, such as E. coli, comprising polynucleotides and compositions containing any of the polynucleotides or polypeptides are also provided.

In another aspect, provided is a method for producing recombinant nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof comprising expressing in a chosen host organism a nucleic acid sequence which encodes said nepenthesin or homologue thereof, and inserting the nucleic acid sequence into an appropriately designed vector. In one aspect, the recombinant nepenthesin is nepenthesin I or a derivative thereof. In one aspect, the recombinant nepenthesin is nepenthesin II or a derivative thereof. In one aspect, the recombinant nepenthesin is a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

In another aspect, provided is a composition comprising recombinant nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof. In one aspect, the recombinant nepenthesin is nepenthesin I or a derivative thereof. In one aspect, the recombinant nepenthesin is nepenthesin II or a derivative thereof. In one aspect, the recombinant nepenthesin is a mixture of nepenthesin I and nepenthesin II or derivatives thereof.

Nepenthesin has two known isoforms: nepenthesin I (known to have two variants nepenthesin Ia and nepenthesin Ib) and II. The sequences of nepenthesin and the nucleotide sequencing of the cDNA encoding nepenthesin are known in the art, for example, described in Athauda S B et al., Enzymic and structural characterization of nepenthesin, a unique member of a novel subfamily of aspartic proteinases, Biochem. J. 381:295-306 (2004). Nepenthesin I mRNA sequences have been described from several species, for example, Nepenthes mirabilis (GenBank Accession No. JX494401), Nepenthes gracilis (GenBank Accession No. AB114914), and Nepenthes alata (GenBank Accession No. AB266803). Nepenthesin II mRNA sequences have been described from several species, for example, Nepenthes mirabilis (GenBank Accession No. JX494402), Nepenthes gracilis (GenBank Accession No. AB114915), and Zea mays (GenBank Accession No. NM_(—)001147869). Nepenthesin I protein sequences have been described from several species, for example, Nepenthes mirabilis (GenBank Accession No. AFV26024), Nepenthes gracilis (GenBank Accession No. BAD07474), Nepenthes alata (GenBank Accession No. BAF98915), and Zea mays (NCBI Reference Sequence: NP_(—)001150925). Nepenthesin II protein sequences have been described from several species, for example, Nepenthes mirabilis (GenBank Accession No. AFV26025), Nepenthes gracilis (GenBank Accession No. BAD07475), and Zea mays (NCBI Reference Sequence: NP_(—)001149229). A putative nepenthesin I protein has been described for Oryza sativa (GenBank Accession No. BAD38020). A putative nepenthesin II protein has been described for Oryza sativa (GenBank Accession No. BAD82000).

Sequence alignment of the known nepenthesin proteins (and putative proteins) is shown in FIG. 9, with corresponding pairwise alignment scores in Table 1. A phylogenetic tree representing the data is shown in FIG. 10. Athauda, et al. further compare nepenthesins with related typical aspartic proteases. Athauda, et al. predicted the backbone structure of nepenthesin Ia based on the structure of porcine pepsin A (nepenthesin Ib and II were predicted to be essentially the same as nepenthesin Ia). The putative catalytic aspartic acid residues were conserved based on this analysis.

In some embodiments, biosynthesis of nepenthesin can be achieved by transforming a cell with a vector comprising a cDNA that encodes nepenthesin I, for example the nucleotide sequence of SEQ ID NO. 1, GenBank Accession No. JX494401, GenBank Accession No. AB114914, or GenBank Accession No. AB266803. In some embodiments, biosynthesis of nepenthesin can be achieved by transforming a cell with a vector comprising a sequence homologous to a cDNA which encodes nepenthesin I, which sequence encodes a protein with protease activity. The sequence may have at least about 60% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 70% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 80% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 85% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 90% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 95% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 96% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 97% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 98% homology to a cDNA that encodes nepenthesin I. The sequence may have at least about 99% homology to a cDNA that encodes nepenthesin I.

In some embodiments, biosynthesis of nepenthesin can be achieved by transforming a cell with a vector comprising a cDNA that encodes nepenthesin II, for example the nucleotide sequence of GenBank Accession No. JX494402 or GenBank Accession No. AB114915. In some embodiments, biosynthesis of nepenthesin can be achieved by transforming a cell with a vector comprising a sequence homologous to a cDNA which encodes nepenthesin II, which sequence encodes a protein with protease activity. The sequence may have at least about 60% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 70% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 80% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 85% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 90% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 95% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 96% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 97% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 98% homology to a cDNA that encodes nepenthesin II. The sequence may have at least about 99% homology to a cDNA that encodes nepenthesin II.

The synthetic nepenthesin such as nepenthesin I and/or nepenthesin II or a derivative thereof can be concentrated or purified according to known methods, such as those for isolating nepenthesin or a derivative thereof from the plant pitcher liquid.

In some embodiments, the protein product isolated from a natural source or a synthetic source comprises at least 20% by weight of nepenthesin or a derivative thereof. In some embodiments, the isolated protein product comprises at least about 50%, about 75%, about 90%, about 95% by weight of nepenthesin or a derivative thereof. In some embodiments, the isolated protein product comprises at least 99% by weight of nepenthesin or a derivative thereof.

In some embodiments, the recombinant nepenthesin comprises substantially only nepenthesin I. In some embodiments, the recombinant nepenthesin comprises substantially only nepenthesin II. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 100:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 90:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 70:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 60:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 50:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 40:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 30:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 20:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 10:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 5:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 4:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 3:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 2:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:1. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:2. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:3. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:4. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:5. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:10. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:20. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:30. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:40. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:50. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:60. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:70. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:80. In some embodiments, recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:90. In some embodiments, the recombinant nepenthesin comprises a ratio of nepenthesin I to nepenthesin II of at least about 1:100.

In some embodiments, the protein product isolated from a natural source or a synthetic source comprises a protein that is at least about 70% homologous to nepenthesin I and retains protease activity. The protein may be at least about 80% homologous to nepenthesin I. The protein may be at least about 85% homologous to nepenthesin I. The protein may be at least about 90% homologous to nepenthesin I. The protein may be at least about 95% homologous to nepenthesin I. The protein may be at least about 96% homologous to nepenthesin I. The protein may be at least about 97% homologous to nepenthesin I. The protein may be at least about 98% homologous to nepenthesin I. The protein may be at least about 99% homologous to nepenthesin I.

In some embodiments, the protein product isolated from a natural source or a synthetic source comprises a protein that is at least about 70% homologous to nepenthesin II and retains protease activity. The protein may be at least about 80% homologous to nepenthesin II. The protein may be at least about 85% homologous to nepenthesin II. The protein may be at least about 90% homologous to nepenthesin II. The protein may be at least about 95% homologous to nepenthesin II. The protein may be at least about 96% homologous to nepenthesin II. The protein may be at least about 97% homologous to nepenthesin II. The protein may be at least about 98% homologous to nepenthesin II. The protein may be at least about 99% homologous to nepenthesin II.

In some embodiments, the protein product isolated from a natural source or a synthetic source comprises nepenthesin or a derivative thereof with at least about 10% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 20% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 30% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 40% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 50% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 60% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 70% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 80% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 90% of the original protease activity of nepenthesin I. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with greater than about 100% of the original protease activity of nepenthesin I.

In some embodiments, the protein product isolated from a natural source or a synthetic source comprises nepenthesin or a derivative thereof with at least about 10% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 20% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 30% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 40% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 50% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 60% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 70% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 80% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with at least about 90% of the original protease activity of nepenthesin II. In some embodiments, the protein product comprises nepenthesin or a derivative thereof with greater than about 100% of the original protease activity of nepenthesin II.

III. EXAMPLES

Unless stated otherwise, the abbreviations used throughout the specification have the following meanings:

-   -   g=gram     -   kDa=kiloDalton     -   kg=kilogram     -   L=liter     -   LC=liquid chromatography     -   mg=milligram     -   min=minute     -   mL=milliliter     -   mM=millimolar     -   MS=mass spectrometry     -   nM=nanomolar     -   pM=picomolar     -   s.d.=standard deviation     -   μCi=microcurie     -   μg microgram     -   μL=microliter     -   μM=micromolar     -   μm=micrometer     -   ° C.=degree Celsius

These one-letter symbols have the following meaning when representing amino acids:

-   -   A=Alanine     -   R=Arginine     -   N=Asparagine     -   D=Aspartic acid     -   C=Cysteine     -   E=Glutamic acid     -   Q=Glutamine     -   G=Glycine     -   H=Histidine     -   I=Isoleucine     -   L=Leucine     -   K=Lysine     -   M=Methionine     -   F=Phenylalanine     -   P=Proline     -   S=Serine     -   T=Threonine     -   W=Tryptophan     -   Y=Tyrosine     -   V=Valine

Example 1 Nepenthesin Extract Preparation Chemicals

Water and acetonitrile, HPLC grade form Burdick and Jackson, were purchased from VWR. Formic acid, Tris, glycine were purchased from Sigma Aldrich.

Plant Culture

Transplants of Nepenthes rafflesiana, Nepenthes ampularia, Nepenthes mirabilis, and Nepenthes globosa were purchased from Keehns Carnivores (accessible via hypertext transfer protocol on the world wide web at keehnscarnivores.ca). These were potted with wood bark, perlite, peat moss and humus (40, 35, 10, 5% respectively). Growth conditions involved 14 hours of light per day, 80% humidity and temperature in the 23-28° C. range with 2 to 3 waterings a week. Upon pitcher maturity, plants were fed with one or two Drosophila per pitcher and the pitcher fluid harvested one week later. Pitchers and their secretions were left to recover for one week prior to a second round of feeding and extraction.

Extract Preparation

Pitcher fluid was collected from all four species of plants and combined. The crude pitcher fluid was first clarified through a 0.22 μm filter, then concentrated 80 to 100 fold using an Amicon Ultra centrifugal 10 kDa molecular weight cut-off filter (both from Millipore). Prior to use in digestions, the concentrate was acid-activated with 100 mM Glycine HCl (pH 2.5) for 3 hours, then washed 3× with 100 mM Glycine-HCl (pH 2.5) in the filtration device, using 10× fluid volume for each wash). The final isolate was then rediluted to an 11× concentration based on the original sampling of pitcher fluid.

Characterization of Pitcher Fluid Extract

The fluidic secretions of the pitcher plant were concentrated and the digestion enzymes activated by pH reduction (pH 2.5). The impact of the enrichment process and the activation on the fluid proteome was determined using proteomics methods. First, to confirm the presence of nepenthesin enzyme, the inactive concentrate was separated by SDS-PAGE. Seven contiguous gel zones with very faint coomassie staining were digested with trypsin and analyzed by nanoLC-MS/MS using standard methods. This is not expected to be a complete catalog of the activated fluid proteome, but the analysis confirmed the presence of the aspartic protease nepenthesin I/II, as well as a glucanase, chitinase, carboxypeptidase and peroxidase of plant origin, plus modest levels of drosophila and bacterial contamination. The low complexity of the fluid proteome is consistent with recent analyses, Hatano N, Hamada T (2012) Proteomic analysis of secreted protein induced by a component of prey in pitcher fluid of the carnivorous plant Nepenthes alata. Journal of Proteomics 3; 75(15):4844-52 (Epub Jun. 15, 2012), but nepenthesin-I was found distributed over a much wider mass range in this analysis (40-70 kDa). The acid-activated fluid was then processed and analyzed in a similar fashion. The activation process reduced the overall protein yield, and also appeared to simplify the composition. Aside from nepenthesin-I, only minor contamination from keratin and actin were in evidence. These analyses point to the low complexity of the enriched fluid, where nepenthesin is the major component. The total protein concentration of the activated and 80× enriched fluid was measured by a BCA assay to be 22 ng/4. This value is consistent with an earlier study describing enrichment of the fluid. Tokes Z A, et al., Digestive Enzymes Secreted by Carnivorous Plant Nepenthes-Macferlanei-L. Planta 119(1):39-46 (1974).

Example 2 Digest Mapping of Proteins by Pepsin and Nepenthesin Extract Nepenthesin Digest Mapping by Mass Spectrometry

Nepenthesin extract was prepared as in Example 1.

Digestions of proteins were carried out in solution using a LEAP HTX-PAL autosampler and dispensing system designed for hydrogen/deuterium exchange (HDX) applications, and data were collected with an AB Sciex Triple-TOF 5600 QqTOF mass spectrometer. Peptides were identified using Mascot (v2.3) from MS/MS data. Briefly, 8 μL of 8 μM protein (XRCC4, XLF, Ligase IV-tandem BRCT domains, PNK, myoglobin, or cytochrome C) were mixed with 10 μL of 11× concentrated fluid for 2 min. at 10° C. Myoglobin and cytochrome C were purchased from Sigma. After dilution to 1 μM substrate concentration, 15 μL were injected into the chilled reversed-phase LC system (4° C.) connected to the mass spectrometer. The peptides were trapped on a 5 cm, 200 μm i.d. Onyx C18 monolithic column (Phenomenex Inc.) and eluted with an acetonitrile gradient from 3% to 40% in 10 minutes. Peptides detected in these analyses were selected for CID fragmentation in multiple information-dependent acquisitions of MS/MS spectra, akin to the gas-phase fractionation strategy. Blonder J, et al., Proteomic investigation of natural killer cell microsomes using gas-phase fractionation by mass spectrometry. Biochimica Et Biophysica Acta-Proteins and Proteomics 1698(1):87-95 (2004). Spectra were searched against a miniature database containing the sequences for all six proteins. Sequencing results were manually verified.

Results

A series of proteins were digested with the enriched fluid under conditions suitable for HDX-MS experiments. The digestion specificity of the concentrate was characterized at the P1 and P1′ positions (FIG. 1), to support a comparison with similar studies applied to pepsin. Hamuro Y, et al., Specificity of immobilized porcine pepsin in H/D exchange compatible conditions. Rapid Communications in Mass Spectrometry 22(7):1041-1046 (2008). In this example, the enzyme-to-substrate ratio was 1:85 based on the assumption that all the measured protein in the enriched fluid is nepenthesin, even though some contaminating proteins were obviously present.

The nepenthesin data represents an assessment of 1612 residues and although not as extensive as the corresponding pepsin data (13,766 residues), the sequence diversity is sufficiently high in the protein set to warrant a comparison at the level of P1 and P1′ positions. The greatest specificity for pepsin appears to be in the P1 position. It presents high-efficiency cleavage for the hydrophobic residues F, L and M but cleavage after P, H, K and R is essentially forbidden. Nepenthesin cleaves after most residues with the exception of G, S, T, V, I and W. It supports a high rate of cleavage after the expected pepsin P1 residues but also at the residues forbidden in pepsin digestion, notably K, R and P. In the P1′ position, pepsin shows a preference for hydrophobic residues in general, including any residue with aromaticity. Conversely, nepenthesin demonstrates little in the way of selectivity at the P1′ position, except perhaps against G, P and H. Overall, nepenthesin demonstrates significantly relaxed specificity at the P1 position relative to pepsin, and provides an indication of very high efficiency.

Example 3 Digest Mapping of Multi-Domain Protein, XRCC4, by Pepsin and Nepenthesin Extract HD Exchange of a Complex Involved in DNA-Damage Repair

Nepenthesin extract was prepared as in Example 1.

Stock solutions of XRCC4 (1-200) with BRCT, and XRCC4 (full length) with BRCT were diluted in buffer (10 mM Tris-HCl, pH 7.5) to equimolar concentrations (10 μM) and incubated at 4° C. for a minimum of 30 min to promote complexation. The samples were held at 4° C. until HDX analysis. Aliquots were deuterated for 2 min at 20° C. with the addition of D₂O (25% v/v). Aliquots were then digested in two ways. In the first digestion strategy, protein deuteration was quenched by adding the sample to chilled 100 mM glycine-HCl (pH 2.5), and the quenched protein solution was injected into a pepsin microreactor. This microreactor was installed in the HTX-PAL system between the injector valve and the C18 column. Protein digest was captured on the monolithic C18 capillary column and eluted into the mass spectrometer. All fluidic elements, including the microreactor, were chilled at 4° C. to minimize deuterium back-exchange during the analysis time (<15 min). In the second digestion strategy, an equivalent amount of deuterated protein was simultaneously quenched and digested with 3 or 5 μL of 11× nepenthes fluid for 3 or 5 min, respectively, at 10° C. The sample was injected into the chilled LC-system connected to the mass spectrometer.

Replicate mass shift measurements were made (4 or more) and referenced to control protein states—free XRCC4 (1-200), free XRCC4 (full length) and free LigIV-BRCT. The average deuterium level for each peptide was determined using Mass Spec Studio (manuscript in preparation), which is a rebuild of Hydra v1.5. Slysz G W, et al., Hydra: software for tailored processing of H/D exchange data from MS or tandem MS analyses. Bmc Bioinformatics 10 (2009). Perturbations in mass shifts were considered significant if (a) they passed a two-tailed t test (p<0.05) using pooled standard deviations from the analyses of each state, (b) they passed a distribution analysis to guard against spectral overlap and (c) they exceeded a threshold shift value (±2 s.d.) based on a measurement of the shift noise and assuming its normal distribution Bennett M J, et al., Discovery and Characterization of the Laulimalide-Microtubule Binding Mode by Mass Shift Perturbation Mapping. Chemistry & Biology 17(7):725-734 (2010).

Results

To determine if relaxed specificity translates into an improvement in sequence mapping for HDX-MS applications, full-length XRCC4, a protein that contains a globular domain, and extended helical stalk, and a long disordered C-terminal was profiled. Hammel M, et al., XLF Regulates Filament Architecture of the XRCC4. Ligase IV Complex. Structure 18(11):1431-1442 (2010); and Junop M S, et al., Crystal structure of the Xrcc4 DNA repair protein and implications for end joining Embo J 19(22):5962-5970 (2000). Such multi-domain proteins are challenging to encompass in a single digestion protocol, and in particular, intrinsically-disordered regions tend to digest poorly with pepsin as they are relatively depleted in hydrophobic residues and enriched in proline and charged residues. Dunker A K, et al. Intrinsically disordered protein. Journal of Molecular Graphics & Modelling 19(1):26-59 (2001). The pepsin and nepenthesin maps for this protein are displayed in FIG. 2. In this comparison, an exhaustive mapping was pursued for both enzymes, using a range of different protease amounts, and recursive MS/MS experiments. Nepenthesin provides superior coverage of the full length protein: 357 peptides for nepenthesin (hatched bars) compared to 187 for pepsin (white bars). (The average peptide length of 11 residues was the same for both enzymes.) Both enzymes represent the globular and stalk regions with a large number of overlapping peptides but the complementarity provided by nepenthesin is evident. For example, nepenthesin offers considerably deeper coverage of a β-sheet region in the globular domain (residues 1-30, FIG. 2A). The disordered C-terminal region is covered to a much greater extent as well, and to a considerably higher level of redundancy (FIG. 2C-D). Each residue in this disordered tail region receives 16× coverage using nepenthesin and only 4.7× coverage with pepsin.

The existence of any bias in peptide detection is explored by selecting average search score as the metric (FIG. 3). The approach emphasizes confidence in sequence identification as the principle means by which sequence maps are defined. One outliner is R. The higher scores for peptides terminating in R likely reflect a combination of higher average peptide intensity and better fragmentation, which is consistent with what we know from trypsin-based bottom-up proteomics. Warwood S, et al. Guanidination chemistry for qualitative and quantitative proteomics. Rapid Communications in Mass Spectrometry 20(21):3245-3256 (2006).

Example 4 Digestion of XRCC4 with Varying Enzyme-to-Substrate Ratios

The enzyme efficiency was examined in greater detail. The degree to which the peptide mass map could be varied, or tuned, simply by altering the enzyme-to-substrate ratio is shown in FIG. 4. Nepenthesin load was varied over a 50-fold range for in-solution digestions. For the pepsin experiment, immobilized pepsin in a slurry format was used rather than free pepsin to avoid extensive pepsin autolysis. The enzyme load was varied over an 8-fold range; lower amounts led to poor peptide intensities and higher amounts had no effect on the map. It was found that nepenthesin generated a very low autolysis profile even at the higher loads. An aggregate peptide ion chromatogram (PIC) was used as a measure of effective digestion. The comparison of the relatively similar distributions found at 0.38:1 (nepenthesin:substrate) with 520:1 (pepsin:substrate) represents a remarkable 1400-fold improvement in efficiency for nepenthesin over pepsin in HDX-like applications.

The nepenthesin digest could be more readily tuned from large fragments to small by varying the enzyme load, and generating a variable representation of XRCC4. This is demonstrated in FIG. 4A by the transition in the PIC from long retention times at low load to short retention times at high load. This transition correlated with the average peptide length for the most abundant peptides shifting from >12 at low enzyme load to 10 at high enzyme load. Conversely, varying pepsin load did not significantly alter the PIC or average peptide length (FIG. 4B). A forced-flow pepsin microreactor may improve tuning but would likely not generate smaller fragments.

Example 5 Digestion of Gliadin by Nepenthesin Extract

Digestions of gliadin by nepenthesin were performed in solution using a LEAP HTX-PAL autosampler and dispensing system designed for hydrogen/deuterium exchange (HDX) applications. Data were collected using an AB Sciex Triple-TOF 5600 QqTOF mass spectrometer. Peptides were identified using Mascot (v2.3) from MS/MS data. Briefly, 12 pmol of crude gliadin (purchased from Sigma Aldrich) were mixed with 2 μL of 100× concentrated extract, produced as described in Example 1. After digestion the entire volume was injected into a reversed-phase LC system connected to the mass spectrometer. The peptides were trapped on a 7 cm, 150 μm i.d. Magic C18 column and eluted with an acetonitrile gradient from 10% to 40% in 10 or 30 minutes. Peptides detected in these analyses were selected for CID fragmentation in multiple information-dependent acquisitions of MS/MS spectra. Spectra were searched against a miniature database containing the sequences for all identified wheat gliadin (α, β, γ, ω) proteins plus the low and high molecular weight glutenin. FIG. 5 shows the average length of all peptides identified from the nepenthesin digestion of gliadin from wheat, using LC-MS/MS, after 1, 5, 10, 15, 30, 60, 130, 360 or 810 minutes at 37° C. A 95% confidence cut-off (p<0.05) on the scores were used to remove false positive identification. Relative standard deviation of the peptide length is shown in the inset figure.

FIG. 6 displays the number of peptides identified by LC-MS/MS after 1, 5, 10, 15, 30, 60, 130, 360 or 810 minutes digestion at 37° C., grouped by length. Data as in FIG. 5.

FIG. 7 displays the same data as in FIG. 5, as a probability of obtaining a certain length after 10, 60, 120, 360 or 810 minutes digestion at 37° C.

Example 6 Nepenthesin Extract Purification Purification of Extract

Sepharose-immobilized pepstatin in a 50×2 cm ID column was equilibrated in 20 mM Glycine-HCl, pH 2.5-3. The filtered pitcher fluid (prepared as described in Example 1) was cycled twice through the column, and the column washed with 100 mL equilibration buffer (20 mM glycine HCl, pH 2.5). The column was eluted with 100 mM ammonium bicarbonate pH 8.7 and fractions collected. In order to preserve maximum the enzyme activity, the pH was decreased to 4 right after fraction collection with 2 M glycine HCl, pH 2.5. Activity was verified using a digestion assay, and the most active fractions combined and concentrated to approximately 80×, based on original fluid volume.

Example 7 Recombinant Nepenthesin I

The gene for nepenthesin I (see SEQ ID NO: 1; encoding amino acid residues 20-413, from N. gracilis, without the plant signal sequence) was prepared from nepenthesin I cDNA, and placed between Ndel and HindIII restriction sites. This sequence was cloned into pET21a, using T4 DNA ligase (1 U) (New England Bio, NEB), T4 DNA ligase buffer (NEB), ATP (0.5 mM) (NEB), 0.5 μg pET21a vector and 2 μg of the nepenthesin I cDNA. This was incubated at 18° C. for 4 hours. The ligation mixture (5 μL) was added to 200 μL of NovaBlue competent cells and incubated on ice for 15 minutes. Cells were transformed by heat shock (45 seconds at 42° C., then immediately on ice, with 1 ml of LB medium) and incubated for 1 hour at 37° C., and plated with antibiotics (tetracycline and ampicillin). After confirming gene presence in several white colonies, a representative colony was chosen for maxiprep. The resulting recombinant plasmid pET21a/R.NepI was transformed into E. coli C41 by heat-shock as above, for expression under induction by IPTG. Here, cells were grown up to an OD₆₆₀ of 0.6 and induced with 0.1 mM IPTG for four hours at 37° C. The expressed protein went to inclusion bodies.

Inclusion bodies were isolated as follows. Cells were centrifuged, sucrose lysis buffer was added (25% saccharose, 50 mM TrisCl pH 7.4, 1 mM EDTA, 1 mM NaN₃, and protease inhibitors), and the cells were subjected to four rounds of freeze/thaw and sonication. This was followed by the addition of DNAse and RNAse for a 30 min. incubation at room temperature. The preparation was centrifuged (˜15 min. at 5000×g) to pellet the inclusion bodies and membrane fragments. This pellet was resuspended in Triton buffer (50 mM TrisCl pH 7.4, 10 mM NaCl, 1 mM β-mercaptoethanol, 1 mM NaN₃, 0.5% Triton X100+protease inhibitors) and sonication performed on ice. This was once again centrifuged, to pellet the inclusion bodies, and the pellet was washed twice on ice (with mixing and sonication) in a buffer free of Triton (50 mM TrisCl pH 7.4, 10 mM NaCl, 1 mM β-mercaptoethanol, 1 mM NaN₃, protease inhibitors).

The protein pellet was then subjected to refolding. One g of inclusion bodies was suspended into 1 L of 50 mM CAPS pH 10.5, 8 M urea, 1 mM EDTA, 1 mM glycine, 500 mM NaCl, 300 mM β-mercaptoethanol and shaken for 1 hr. The suspension was dialysed against 50 mM Tris, pH 11, twice for 1 hour at a time, followed by one day of dialysis against 50 mM Tris, pH 7.5, and finally, dialysis against phosphate buffer with 300 mM NaCl, pH 7.0.

The solution was centrifuged at high speed (10000×g for 15 min.) to remove any un-refolded protein, and the supernatant filtered through a 0.22 μm membrane. Nepenthesin I was activated at pH 2.5 (glycine-HCl) overnight at 4° C. Yields range from 10 to 100 mg of folded, activated protein, starting from 1 L of cell culture.

Example 8 Recombinant Nepenthesin II

The cDNA of nepenthesin II (from N. gracilis, without the plant signal sequence) was used to prepare nepenthesin II cDNA. This sequence was cloned into pET21a between Ndel and HindIII restriction sites, using T4 DNA ligase (1 U) (New England Bio, NEB), T4 DNA ligase buffer (NEB), ATP (0.5 mM) (NEB), 0.5 μg pET21a vector and 2 μg of the nepenthesin II cDNA. This was incubated at 18° C. for 4 hours. The ligation mixture (5 μL) was added to 200 μL, of NovaBlue competent cells and incubated on ice for 15 minutes. Cells were transformed by heat shock (45 seconds at 42° C., then immediately on ice, with 1 ml of LB medium) and incubated for 1 hour at 37° C., and plated with antibiotics (tetracycline and ampicillin). After confirming gene presence in several white colonies, a representative colony was chosen for maxiprep. The resulting recombinant plasmid pET21a/R.NepI was transformed into E. coli C41 by heat-shock as above, for expression under induction by IPTG. Here, cells were grown up to an OD₆₆₀ of 0.6 and induced with 0.1 mM IPTG for four hours at 37° C. The expressed protein went to inclusion bodies.

Inclusion bodies were isolated as follows. Cells were centrifuged, sucrose lysis buffer was added (25% saccharose, 50 mM TrisCl pH 7.4, 1 mM EDTA, 1 mM NaN₃, and protease inhibitors), and the cells were subjected to four rounds of freeze/thaw and sonication. This was followed by the addition of DNAse and RNAse for a 30 min. incubation at room temperature. The preparation was centrifuged (˜15 min. at 5000×g) to pellet the inclusion bodies and membrane fragments. This pellet was resuspended in Triton buffer (50 mM TrisCl pH 7.4, 10 mM NaCl, 1 mM β-mercaptoethanol, 1 mM NaN₃, 0.5% Triton X100+protease inhibitors) and sonication performed on ice. This was once again centrifuged, to pellet the inclusion bodies, and the pellet was washed twice on ice (with mixing and sonication) in a buffer free of Triton (50 mM TrisCl pH 7.4, 10 mM NaCl, 1 mM β-mercaptoethanol, 1 mM NaN₃, protease inhibitors).

The protein pellet was then subjected to refolding. One g of inclusion bodies was suspended into 1 L of 50 mM CAPS pH 10.5, 8 M urea, 1 mM EDTA, 1 mM glycine, 500 mM NaCl, 300 mM β-mercaptoethanol and shaken for 1 hr. The suspension was dialysed against 50 mM Tris pH 11 twice for 1 hour at a time, followed by one day of dialysis against 50 mM Tris pH 7.5, and finally, dialysis against phosphate buffer with 300 mM NaCl, pH 7.0.

The solution was centrifuged at high speed (10000×g for 15 min.) to remove any un-refolded protein, and the supernatant filtered through a 0.22 μm membrane. Nepenthesin II was activated at pH 2.5 (glycine-HCl) overnight at 4° C. Yields range from 10 to 100 mg of folded, activated protein, starting from 1 L of cell culture.

Example 9 Digest Mapping of Gliadin by Nepenthesin

Nepenthesin extract was prepared as described in Example 1. Purified nepenthesin extract was prepared as described in Example 6. Recombinant nepenthesin I was prepared as described in Example 7.

Gliadin digestion was performed as described in Example 5, except that the substrate to enzyme ratio was approximately 1000:1. Gliadin was digested at 37° C. for 2 hr with nepenthesin extract, purified nepenthesin extract, or recombinant nepenthesin I.

Gliadin is a class of proteins found in wheat and other cereal grains. Gliadins are highly enriched in proline and glutamine residues. We have determined that recombinant nepenthesin I digests gliadin protein very effectively at pH 2-3. The P1 cleavage preference of recombinant nepenthesin I is very similar to that of the concentrated fluid extract, as well as the purified fraction of the extract (FIG. 8A). Surprisingly, the extract showed a higher preference for glutamine than either the purified extract or recombinant nepenthesin I.

The P1 cleavage preference of recombinant nepenthesin I is very similar to that of the concentrated fluid extract, as well as the purified fraction of the extract (FIG. 8B). Surprisingly, the extract showed a higher preference for proline than either the purified extract or recombinant nepenthesin I.

The extract contains both nepenthesin I and II, but the purification strategy recovers far less active nepenthesin II than nepenthesin I. Without wishing to be bound by theory, it is believed that the heightened cleavage at the P1 glutamine position and the P1′ proline position by the extract are due to nepenthesin II and/or to synergy between nepenthesin I and nepenthesin II.

Example 10 Comparison of Nepenthesin Proteins

The protein sequences of known and putative nepenthesin proteins were aligned using Clustal 2.1 Multiple Sequence Alignment. The sequences of nepenthesin I were: Nepenthes mirabilis (GenBank Accession No. AFV26024), Nepenthes gracilis (GenBank Accession No. BAD07474), Nepenthes alata (GenBank Accession No. BAF98915), Zea mays (NCBI Reference Sequence: NP 001150925), and Oryza sativa (GenBank Accession No. BAD38020). The sequences of nepenthesin II were: Nepenthes mirabilis (GenBank Accession No. AFV26025), Nepenthes gracilis (GenBank Accession No. BAD07475), Zea mays (NCBI Reference Sequence: NP_(—)001149229). and Oryza sativa (GenBank Accession No. BAD82000). The resulting alignment is shown in FIG. 9. FIG. 10 shows a phylogenetic tree indicating the relatedness of nepenthesin proteins between different species. Table 1 shows the pairwise alignment scores between each sequence.

TABLE 1 Sequence 1 Sequence 2 Score N. mirabilis nepenthesin I N. mirabilis nepenthesin II 65 N. mirabilis nepenthesin I N. gracilis nepenthesin I 94 N. mirabilis nepenthesin I N. gracilis nepenthesin II 66 N. mirabilis nepenthesin I N. alata nepenthesin I 99 N. mirabilis nepenthesin I O. sativa nepenthesin I 39 N. mirabilis nepenthesin I O. sativa nepenthesin II 24 N. mirabilis nepenthesin I Z. mays nepenthesin I 39 N. mirabilis nepenthesin I Z. mays nepenthesin II 26 N. mirabilis nepenthesin II N. gracilis nepenthesin I 64 N. mirabilis nepenthesin II N. gracilis nepenthesin II 96 N. mirabilis nepenthesin II N. alata nepenthesin I 65 N. mirabilis nepenthesin II O. sativa nepenthesin I 37 N. mirabilis nepenthesin II O. sativa nepenthesin II 24 N. mirabilis nepenthesin II Z. mays nepenthesin I 36 N. mirabilis nepenthesin II Z. mays nepenthesin II 23 N. gracilis nepenthesin I N. gracilis nepenthesin II 66 N. gracilis nepenthesin I N. alata nepenthesin I 94 N. gracilis nepenthesin I O. sativa nepenthesin I 40 N. gracilis nepenthesin I O. sativa nepenthesin II 25 N. gracilis nepenthesin I Z. mays nepenthesin I 38 N. gracilis nepenthesin I Z. mays nepenthesin II 26 N. gracilis nepenthesin II N. alata nepenthesin I 66 N. gracilis nepenthesin II O. sativa nepenthesin I 38 N. gracilis nepenthesin II O. sativa nepenthesin II 27 N. gracilis nepenthesin II Z. mays nepenthesin I 39 N. gracilis nepenthesin II Z. mays nepenthesin II 23 N. alata nepenthesin I O. sativa nepenthesin I 39 N. alata nepenthesin I O. sativa nepenthesin II 25 N. alata nepenthesin I Z. mays nepenthesin I 39 N. alata nepenthesin I Z. mays nepenthesin II 26 O. sativa nepenthesin I O. sativa nepenthesin II 28 O. sativa nepenthesin I Z. mays nepenthesin I 35 O. sativa nepenthesin I Z. mays nepenthesin II 23 O. sativa nepenthesin II Z. mays nepenthesin I 24 O. sativa nepenthesin II Z. mays nepenthesin II 15 Z. mays nepenthesin I Z. mays nepenthesin II 26

The data as set forth in the examples above demonstrate that nepenthesin, either as a mixture or purified or recombinant components thereof, efficiently digest gluten, whereas pepsin does not. Accordingly, this invention provides for a method to allow for the digestion of gluten in a protein comprising gluten by use of a mixture of nepenthesin or purified or recombinant components thereof.

Although the foregoing has been described in some detail by way of illustration and example for purposes of clarity of understanding, one of skill in the art will appreciate that certain changes and modifications may be practiced within the scope of the appended claims. In addition, each reference provided herein is incorporated by reference in its entirety to the same extent as if each reference was individually incorporated by reference. 

1.-44. (canceled)
 45. A composition suitable for treating celiac disease, the composition comprising a pharmaceutically acceptable excipient and an effective amount of nepenthesin so as to treat celiac disease in a patient in need thereof, wherein the nepenthesin is in an inactive form.
 46. The composition of claim 45 which is at a pH of about or above
 5. 47. The composition of claim 45 which is in an aqueous formulation.
 48. The composition of claim 47 which is sterile.
 49. The composition of claim 47 which is in a form selected from the group consisting of a solution, a suspension, an emulsion, a capsule, and a syrup.
 50. The composition of claim 45 which is in a solid formulation.
 51. The composition of claim 50 which is in a form selected from the group consisting of a tablet, a pill, a capsule, a powder, and a sustained release formulation.
 52. The composition of claim 45, wherein the nepenthesin comprises recombinant nepenthesin I, recombinant nepenthesin II, or a mixture thereof.
 53. The composition of claim 45, wherein the nepenthesin comprises a fragment of nepenthesin which retains proteolytic activity.
 54. The composition of claim 53, wherein the fragment of nepenthesin has at least about 20 contiguous amino acids of the full nepenthesin protein. 